In http://docs.mongodb.org/manual/core/replica-set-sync/ a few sections can be updated for new storage engines.
Is this true for all storage engines from the "Multithreaded Replication" section. If it is true then it limits my ability to have long running queries on a replica that isn't getting far behind on replication.
'While applying a batch, MongoDB blocks all reads. As a result, secondaries can never return data that reflects a state that never existed on the primary.'
The "Prefetching Indexes" section is only true for mmapv1, which is explained in the docs for the referenced parameter, secondaryIndexPrefetch, but I think the docs here could be updated.